Fukushima City, Japan — They don't come much greener than Michio Sato. A science professor at Fukushima University, he has put windmills on his office roof to power his lights and runs his car on biofuel he makes himself.

But even he is conflicted about the value of nuclear energy. "For the sake of energy security and reducing greenhouse gases, I think the very safest plants should be allowed to operate," he says. "But I wonder whether even the safest ones are safe enough."

That dilemma is troubling everyone here, from ordinary citizens to cabinet ministers, as the country's nuclear plants go off-line one by one in the wake of the earthquake and subsequent tsunami that hit the Fukushima Daiichi nuclear power plant on March 11, 2011, causing three reactors to leak radiation.

A year ago, Japan depended on its 54 reactors for 30 percent of its electricity; only two of them remain open, and they will be shut by the end of April. Japan could become the first industrial society to enter the postnuclear age.

The forces gathered against that prospect are powerful: The nuclear industry and utility companies are lobbying hard for the government to allow the plants to reopen soon, warning of economic disaster should power shortages cripple Japan's industry. Their pressure will be "almost unimaginable," says Shaun Burnie, an expert on Japan's nuclear program with Friends of the Earth, an antinuclear group.

Two-thirds want other energy

The Japanese public, however, sensitive both to the legacy of Hiroshima and to the risks that the Fukushima accident underlined, is strongly opposed to any continued dependence on nuclear power. Polls over the past year have found about two-thirds of respondents favor other energy sources.

That sets up a debate whose outcome will shape Japan's future, a debate that is still unresolved at the highest levels of government. For the moment, says Tsutomu Toichi, an adviser to the Institute for Energy Economics think tank here, "nobody can predict what will happen. Nobody knows how many nuclear plants may be reopened, and if so, when."

For the past year, as nuclear reactors have come off-line for refueling, routine maintenance, or by government request, Japanese utilities have made up for most of their lost electricity by boosting the amount they generate in plants fired by gas, oil, or coal.

That is unsustainable, they say, because it is costing them billions of dollars to import fossil fuels, and the government has not yet let them raise prices to consumers. "All the electricity utilities are losing money," says Dr. Toichi, whose think tank is funded by the power companies.

If electricity prices rose, "it would be a problem for the government and the entire economy," adds Kaname Ogawa, deputy head of policy planning at the electricity department of the Ministry of Economy, Trade, and Industry (METI), which oversees the nuclear industry.

METI is predicting a 9 percent shortfall in electricity supplies nationwide next summer if no nuclear plants are reopened, which could mean power cuts. Businesses and households in the Tokyo area achieved greater energy savings than that last summer, galvanized by a government campaign, "but we don't know if all of Japan can survive like Tokyo did," says Mr. Ogawa.

However the politics play out, it seems highly unlikely that any reactors will be on line by this summer. All of them have to undergo new government-mandated stress tests to ensure their resilience to seismic events; so far only two have finished them, and seven months into the process the Nuclear Safety Commission is still reviewing their results. Operators of 34 reactors have not even applied to do the tests yet.

Even if reactors pass their tests, the authorities still have to make the political decision whether to allow them to reopen.

'Political hot potato'

Prime Minister Yoshihiko Noda has said a select group of cabinet ministers will decide: To reassure the public, he may want to wait until the nuclear safety agency he hopes to establish in April is set up and has issued stricter regulations. The opposition, however, objects to his plan for such an agency, and parliament has not yet begun to debate the proposal.

Nor does the decision rest only in the hands of the national government. Governors of prefectures where the nuclear plants are located have the power to block their restart, and they have to take their constituents' views into account. In the current antinuclear mood, "governors are under very strong pressure from below not to agree," says Masaru Kohno, a professor of politics at Waseda University in Tokyo.

Toichi adds, "It's a political hot potato. Nobody wants to take responsibility."

Green can't fill gap yet

Still, advocates of green energy, such as hydropower, solar, and wind, are not hopeful that such sources will replace nuclear power soon.

Even if the government achieves its goal of increasing the share of renewable sources in Japan's energy mix from its current 3.4 percent to 10 percent by 2020, "that won't have much impact on the national situation compared to what nuclear plants have provided" in the past, points out Professor Sato. "It's like an elephant and an ant," he says. "We need to increase the number of ants as quickly as possible."

But so far, laments Tetsunari Iida, head of the Institute for Sustainable Energy Policies, a green think tank in Tokyo, “there is little sign that the current government is ready to do that.”